Low-rank coals, such as lignite and subbituminous coal, usually contain relatively large quantities of water (i.e., about 10 to 50% by weight), which makes the economics of transporting and combusting these coals considerably more expensive than higher rank coals. Furthermore, this high moisture content makes the low-rank coals dangerous due to the possibility of spontaneous combustion during transportation or storage. Conventional drying processes prior to transportation or storage do not solve this problem because the coal will usually regain all of or most of the moisture from the atmosphere over a short period of time. In some cases the reabsorption of moisture causes the coal to become even more pyroforic than prior to drying. However, because of the generally low sulfur content of these low-rank coals, continued and increasing use of these coals may be unavoidable, due to the increasingly stringent regulations on sulfur emission in coal combusting installations. Therefore, there is a need for an inexpensive method for beneficiation of low-rank coals to remove moisture and improve transportation and storage characteristics which obviate or substantially reduces the above problems.
It is thus an object of the present invention to provide a method for beneficiating low-rank coals to remove moisture from these coals.
It is a further object of the present invention to recover surface-modified coal fines which are generated from coal de-watering processes.
It is yet another object of the present invention to provide a method for recovering by agglomeration surface-modified coal fines derived from low-rank coals.
These and other objects of the invention will become apparent to those skilled in the art from the following description, appended claims and drawings, as well as from the practice of the invention.